I have been working for some time to find away that someone can control things without using their hands. Currently there are several tongue interfaces available but all of them are using HALL or other magnetic sensors, and rely on the wearer using a magnet attached to their tongue somehow.
To get the form I took an alginate impression of my upper mouth and cast it in plaster. However your local dentist will do that for about $70. Once you have the impression you can use any thermo plastic to create the shape and test it with some denture glue for fitting.
I wanted to try a different way and found some very nice switches from Panasonic (EVQ-Q2B01W series) that have an very light touch to activate plus it has a excellent tactile 'click' feel. Also for the joystick I found that if I take it apart I can remove one of the contact plates (it has 2) and make it likewise easy to move with the tongue (https://www.sparkfun.com/products/10063
Using an 74HC4067 SMD I can have a maximum of 16 switches (11 around the edge and 5 for the joystick) Of course it is up to the user's end requirement how many of the lines are used. One side of the switches are pulled LOW to ground and the other goes to an input line of the 74HC4067. The output of the 74HC4067 is pulled HIGH. Likewise any of the switches can be replaces with something like a Force Sensitive Resistor (https://www.sparkfun.com/products/9673
) which can detect a range of pressure changes.
At this point one can use either a DFRobot Beetle, or a RFDuino as the embedded controller. Both will fit easily in the interface.
The 4 GPIO pins (RFDuino) or pins 15 to 18 on the DFRobot Beetle (you will have to make one of the Analogs an Digital Output) control the 74HC4067. If you can spare an additioal line then you can control the Enable too. or just pull that to LOW.
Then you can count in binary 0 to 15 through those outputs and read the input to see if it is below 250. If it is then we have a pushed button and can act accordingly.
The rest is essentially up to the application and the user. For myself I will be controlling animatronics inside a costume and not require any additional helpers. For the handicapped it can control wheelchairs etc. For the engineer it can act as a pseudo keyboard changing a HUD to display information whilst they are working with their hands.
This is a picture of my finished module without the controller attached yet. Once attached one can power/communicate either with a cable. Or use the Bluetooth function and a lipo battery suitably insulated and sitting in the cheek.
All surfaces are coated with a silicone 'wash' to give a thin insulating layer.